The present invention relates to a magnetic head which is used for writing to, and reading from, a magnetic recording medium, and a method of manufacturing the same.
In a hard disk drive, data on a recording medium is read or written by a magnetic head. In order to increase the magnetic disk's recording capacity per unit area, a higher areal density is needed. However, the existing longitudinal recording method has a problem that as the recorded bit length decreases, it becomes difficult to increase the areal density due to thermal fluctuation in medium magnetization. A solution to this problem is a perpendicular recording method whereby magnetization signals are recorded in a direction perpendicular to the medium. In the perpendicular recording method, the following types of read head may be used: a GMR head (Giant magnetoresistive head), TMR head (Tunneling giant magnetoresistive head) which provides higher reproduction output, and a CPP (Current perpendicular to the plane) type GMR head in which current flows perpendicularly to the film surface.
In the perpendicular recording method, in order to increase the areal density, the track density and the linear density must be improved as well. In order to improve the linear density, the write head's field gradient must be improved. One method of improving the field gradient is to use a double-layered recording medium having a soft under layer as the lower layer and use, as a write head, a single pole type head which has a main pole and a return pole. However, in order to achieve a high areal density of 200 Gb/in2, the field intensity of the write head must be improved.
Methods of increasing the field intensity include: (1) increasing the cross-sectional area of the air bearing surface of the main pole; and (2) reducing the throat height. The cross-sectional area of the main pole is the product of the track width and the main pole height. The track width must be decreased in order to achieve a high areal density. As for the main pole height, a problem inherent in perpendicular recording might arise that if there is a skew angle in the head, data is written with a side face of the main pole. For this reason, the height is limited to the same level as the track width. On the other hand, there is no limitation to decreasing the throat height. However, because the throat height depends on alignment accuracy on a wafer and air bearing surface processing accuracy, it is difficult not only to reduce the throat height but also to achieve a high accuracy. The throat height which is now needed is approximately 300 nm or less and a processing accuracy of ±50 nm is needed.
The air bearing surface of a head is processed using an ELG (Electro Lapping Guide) element as a processing detection pattern. For example, JP-A No. 67408/2000 discloses a method which uses two ELGs.